Any of various marine mollusks of the class Cephalopoda, such as the octopus, squid, cuttlefish, or nautilus, having a large head, large eyes, prehensile tentacles, and, in most species, an ink sac containing a dark fluid used for protection or defense.

• 头足纲动物软体动物门的一种海生软体动物，如章鱼、鱿鱼、乌贼或鹦鹉螺，有可缠绕的触须、较大的头和眼，大多数种类都有一个作保护或防卫用的容纳深色液体的内存墨囊